Stepped down aftertreatment device shroud

ABSTRACT

A shroud ( 102 ) for an aftertreatment device ( 100 ) for treating exhaust gas from an internal combustion engine comprises a stepped conduit ( 126 ) configured to be disposed over an upper surface of the aftertreatment device ( 100 ) and extending over substantially the entire length of the aftertreatment device ( 100 ), wherein the stepped conduit ( 126 ) is configured to channel a flow of cleaning air longitudinally along the outer and upper surface of the aftertreatment device ( 100 ), wherein an inner surface of the stepped conduit ( 126 ) defines at least a first downwardly extending step ( 134, 136, 138 ) and a second downwardly extending step ( 134, 136, 138 ) that are spaced apart along the length of the aftertreatment device ( 100 ), to direct at least a portion of the flow of cleaning air downward.

FIELD OF THE INVENTION

This invention relates to internal combustion engines. Moreparticularly, it relates to aftertreatment devices for internalcombustion engines. Even more particularly, it relates to shrouds foraftertreatment devices.

BACKGROUND OF THE INVENTION

Modern internal combustion engines are provided with aftertreatmentdevices that process the exhaust gases to remove impurities. Theseaftertreatment devices operate at elevated temperatures and in dirtysurroundings. They must be kept clean in order not to accumulatecombustible matter that can catch fire and damage the aftertreatmentdevice. For this reason, aftertreatment devices may be enclosed ininsulated chambers, or provided with a supply of air that flows acrosstheir surface in order to keep combustible material fro being depositedon the surface.

In one arrangement, an aftertreatment device was provided with a shroudthat defined an elongate plenum extending along the length of theaftertreatment device. Below this plenum a wall with several apertureswas provided. Air entering the plenum could freely travel the length ofthe plenum, and its force, direction, and intensity was controlled bythe location of the apertures formed in the wall.

One problem with this arrangement is that impurities, dust, dirt andother combustible particles are deposited on the wall and graduallyblock the apertures themselves. Furthermore, the arrangement of a plenumenclosed at its bottom by a pierced wall reduced the power of theairflow and prevented it from thoroughly scrubbing the upper surfaces ofthe aftertreatment device.

What is needed, therefore, is a new arrangement of an aftertreatmentdevice shroud that provides for greater airflow, and better cleaningability of the air and also reduces potential blockages of the airflow.

It is an object of this invention to provide such an arrangement.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a shroud (102) for anaftertreatment device (100) for treating exhaust gas from an internalcombustion engine is provided, the shroud comprising: a stepped conduit(126) configured to be disposed over an upper surface of theaftertreatment device (100) and extending over substantially an entirelength of the aftertreatment device (100), wherein the stepped conduit(126) is configured to channel a flow of cleaning air longitudinallyalong an outer and upper surface of the aftertreatment device (100),wherein an inner surface of the stepped conduit (126) defines at least afirst downwardly extending step (134, 136, 138) and a second downwardlyextending step (134, 136, 138) that are spaced apart along a length ofthe aftertreatment device (100), to direct at least a portion of theflow of cleaning air downward.

The shroud ay further comprise a first sidewall (118) that is fixed tothe stepped conduit (126) along a first longitudinal side edge of thestepped conduit (126), wherein the first sidewall (118) extends aroundand encloses a first side surface of the aftertreatment device (100),wherein the first sidewall (118) is disposed to provide a narrow gap(128) between the first sidewall (118) and the first side surface of theaftertreatment device (100) to receive the flow of cleaning air from thestepped conduit (126) over substantially the entire length of theaftertreatment device (100) and to direct the flow of cleaning airgenerally downward over the first side surface of the aftertreatmentdevice (100).

The shroud may further comprise a second sidewall (120) that is fixed tothe stepped conduit (126) along a second longitudinal side edge of thestepped conduit (126) and is disposed on an opposite side of the steppedconduit (126) from the first sidewall (118), wherein the second sidewall(120) extends around and encloses a second side surface of theaftertreatment device (100), wherein the second sidewall (120) isdisposed to provide a narrow gap (130) between the second sidewall (120)and the second side surface of the aftertreatment device (100) toreceive the flow of cleaning air from the stepped conduit (126) oversubstantially the entire length of the aftertreatment device (100) andto direct the flow of cleaning air generally downward over the secondside surface of the aftertreatment device (100).

The aftertreatment device may be elongate, generally cylindrical, andmay have a central longitudinal axis (104) that extends generallyhorizontally.

5. The shroud (102) of claim 4, wherein the aftertreatment device (100)has a top surface, and wherein the stepped conduit (126) extendsgenerally horizontally and is disposed immediately over the top surfaceof the aftertreatment device (100).

The first downwardly extending step (134, 136, 138) and the seconddownwardly extending step (134, 136, 138) maybe disposed above the topsurface of the aftertreatment device (100) and maybe spaced apart alongthe top surface of the aftertreatment device (100).

The first downwardly extending step (134, 136) maybe disposedimmediately downstream of a first protrusion (150, 152) that extendsupwardly from the top surface of the aftertreatment device (100).

The second downwardly extending step (134, 136) maybe disposedimmediately downstream of a second protrusion (150, 152) that extendsupwardly fro the top surface of the aftertreatment device (100).

Each of the first protrusion (150, 152) ad the second protrusion (150,152) may comprise a an annular ring extending about a circumference ofthe aftertreatment device (100).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective left side view of an aftertreatment deviceshroud enclosing an aftertreatment device in accordance with the presentinvention.

FIG. 2 is a perspective right side view of the aftertreatment deviceshroud of FIG. 1.

FIG. 3 is a bottom view of the aftertreatment device shroud of FIGS.1-2.

FIG. 4 is a vertical cross-sectional view of the aftertreatment deviceof FIGS. 1-3 taken at section line 4-4 in FIG. 1. The cutting planedefining the view of FIG. 4 extends perpendicular to a longitudinal axisof the aftertreatment device and of the aftertreatment device shroud.

FIG. 5 is a vertical cross-sectional view of the aftertreatment deviceof FIGS. 1-4 taken at section line 5-5 in FIG. 1. The cutting planedefining the view of FIG. 5 extends perpendicular to a longitudinal axisof the aftertreatment device and of the aftertreatment device shroud.

FIG. 6 is a cross-sectional view of the aftertreatment device of FIGS.1-5 taken at section line 6-6 in FIG. 1. The cutting plane defining theview of FIG. 6 extends vertically and extends longitudinally through thecentral longitudinal axis of the aftertreatment device.

DETAILED DESCRIPTION

The aftertreatment device and the shroud described herein aremirror-symmetric about the vertically and longitudinally extendingcutting plane of FIG. 6.

In the Figures herein, an aftertreatment device 100 is disposed in ashroud 102. The body of the aftertreatment device 100 is generallycylindrical and has a longitudinal central axis 104. An input exhaustconduit 106 that is generally cylindrical extends upward from acylindrical side wall of the aftertreatment device 100 at a first end108 of the aftertreatment device 100. An output exhaust conduit 110 thatis generally cylindrical extends outward from the aftertreatment device100 at a second end 112 of the aftertreatment device 100. The outputexhaust conduit 110 is coaxial with the longitudinal central axis 104 ofthe aftertreatment device 100.

Exhaust gas is introduced into the input exhaust conduit 106. Theexhaust gas then traverses the body of the aftertreatment device 100.The exhaust gas that exits the aftertreatment device 100 through theoutput exhaust conduit 110.

The shroud 102 surrounds substantially the entire aftertreatment device100. The shroud 102 is formed of a single layer of sheet metal. Theshroud 102 is spaced away from the outer surface of the aftertreatmentdevice 100 to permit air introduced into the shroud 102 to flow oversubstantially the entire surface of the aftertreatment device 100.

This airflow performs a dual function. The air flow cools the innersurface of the shroud 102, thereby decreasing the temperature of theshroud 102 and reducing the risk of fire. The airflow also prevents theformation of a layer of combustible matter on the outer surface of theaftertreatment device 100.

The shroud 102 comprises an air inlet 114 is configured to receive airand conduct the air into the shroud 102 and across the upper surface ofthe aftertreatment device 100. The air inlet 114 is located immediatelyadjacent to the input exhaust conduit 106 such that it directs air in ahorizontal direction around both sides of the input exhaust conduit 106.

The shroud 102 further comprises a shell 116. The shell 116 comprises afirst sidewall 118, a second sidewall 120, a first endwall 122, a secondendwall 124 and a stepped conduit 126.

The first sidewall 118 extends substantially the entire length of theaftertreatment device 100. The first sidewall 118 wraps around andencloses a first side of the aftertreatment device 100. The firstsidewall 118 and the first side extend generally vertically. The firstsidewall 118 is spaced slightly away from the first side of theaftertreatment device 100 in order to provide a narrow gap 128 betweenthe first sidewall 118 and the first side of the aftertreatment device100. The gap 128 forms an air channel that maintains a relativelyconstant airflow over substantially the entire first side of theaftertreatment device 100.

The second sidewall 120 extends substantially the entire length of theaftertreatment device 100. The second sidewall 120 wraps around andencloses a second side of the aftertreatment device 100. The secondsidewall 120 and the second side extend generally vertically. The secondsidewall 120 is spaced slightly away from the second side of theaftertreatment device 100 in order to provide a narrow gap 130 betweenthe second sidewall 120 and the second side of the aftertreatment device100. The gap 130 forms an air channel that maintains a relativelyconstant airflow over substantially the entire second side of theaftertreatment device 100.

An elongate outlet 132 is provided between the bottom edge of the firstsidewall 118 and the second sidewall 120. The elongate outlet 132extends substantially the entire length of the aftertreatment device100.

The elongate outlet 132 provides a flow path for air that is introducedinto the air inlet 114 to escape from the space defined between theinner surface of the shroud 102 and the outer surface of theaftertreatment device 100.

The ends of the shroud 102 are defined by the first endwall 122 and thesecond endwall 124 which enclose the ends of the aftertreatment device100.

The first endwall 122 is fixed to the first sidewall 118, the secondsidewall 120, and the input exhaust conduit 106 to enclose the first end108 of the aftertreatment device 100.

The second endwall 124 is fixed to the first sidewall 118, the secondsidewall 120, and the stepped conduit 126 to enclose the second end 112of the aftertreatment device 100.

The stepped conduit 126 forms the upper surface of the shroud 102. Thestepped conduit 126 encloses the upper surface of the aftertreatmentdevice 100. The stepped conduit 126 is fixed to and extends between theupper edges of the first sidewall 118 and the second sidewall 120. Thestepped conduit 126 extends substantially the entire length of theaftertreatment device 100 and is spaced away from the aftertreatmentdevice 100 a distance substantially larger than the gap 128 or the gap130.

Due to this larger spacing, the stepped conduit 126 has a decreasedresistance to airflow in a direction parallel to the longitudinal extentof the aftertreatment device 100. This decreased resistance permits airto flow from the air inlet 114 at the first end 108 of theaftertreatment device 100, down the length of the stepped conduit 126 tothe second end 112 of the aftertreatment device 100.

The cross-sectional area between the stepped conduit 126 and the topsurface of the aftertreatment device 100 decreases over the length ofthe aftertreatment device 100 as the stepped conduit 126 extends fromthe first end 108 to the second end 112.

The cross-sectional area between the stepped conduit 126 and the surfaceof the aftertreatment device 100 over which it extends does not decreasegradually and uniformly over the length of the stepped conduit 126,however. It decreases in a stepwise fashion. To provide this stepwisereduction the inner surface (and in this case the outer surface as well,since the stepped conduit 126 is formed of a single layer of sheetmetal) is provided with a series of three downward steps (a step 134, astep 136, and a step 138) in a top surface 140 of the stepped conduit126, as well as a laterally inward step 142 on a first side surface 144of the stepped conduit 126 and an opposing laterally inward step 146 ona second side surface 148 of the stepped conduit 126. The laterallyinward step 146 is on an opposing side of the stepped conduit 126 fromthe laterally inward step 142 o the first side surface 144.

The effect of these step changes in the inner surface of the steppedconduit 126 is to cause a disruption in the smooth flow of the airtraveling longitudinally down the stepped conduit 126. This disruptionin the flow of air directs a greater portion of the air downward intothe gap 128 and gap 130.

This downward flow improves the scouring of the upper surface of theaftertreatment device 100. The scouring both removes pockets ofotherwise combustible material that may have accumulated on the uppersurface of the aftertreatment device 100. It also helps prevent theformation the formation of pockets of material on the upper surface ofthe aftertreatment device 100. The upper surface of the aftertreatmentdevice 100 has protrusions extending upwardly therefrom. The protrusionscomprise a first circumferential ring 150 and the second circumferentialring 152. In previous arrangements, dust and other combustible particleswould accumulate on the upper and side surfaces of the aftertreatmentdevice 100 downstream of these protrusions. The steps described herein.

It should be understood that the particular arrangements shown anddescribed in this document are not the only ways in which the inventioncan be created. The arrangements shown in this document are thecurrently preferred embodiments of the invention. However, one skilledin the art of agricultural harvester design and manufacture can readilysee other variations that would also be protected by the claims of thisdocument.

I claim:
 1. A shroud (102) for an aftertreatment device (100) fortreating exhaust gas from an internal combustion engine, the shroudcomprising: a stepped conduit (126) configured to be disposed over anupper surface of the aftertreatment device (100) and extending oversubstantially an entire length of the aftertreatment device (100),wherein the stepped conduit (126) is configured to channel a flow ofcleaning air longitudinally along an outer and upper surface of theaftertreatment device (100), wherein an inner surface of the steppedconduit (126) defines at least a first downwardly extending step (134,136, 138) and a second downwardly extending step (134, 136, 138) thatare spaced apart along a length of the aftertreatment device (100), todirect at least a portion of the flow of cleaning air downward.
 2. Theshroud (102) of claim 1, further comprising a first sidewall (118) thatis fixed to the stepped conduit (126) along a first longitudinal sideedge of the stepped conduit (126), wherein the first sidewall (118)extends around and encloses a first side surface of the aftertreatmentdevice (100), wherein the first sidewall (118) is disposed to provide anarrow gap (128) between the first sidewall (118) and the first sidesurface of the aftertreatment device (100) to receive the flow ofcleaning air from the stepped conduit (126) over substantially theentire length of the aftertreatment device (100) and to direct the flowof cleaning air generally downward over the first side surface of theaftertreatment device (100).
 3. The shroud (102) of claim 2, furthercomprising a second sidewall (120) that is fixed to the stepped conduit(126) along a second longitudinal side edge of the stepped conduit (126)and is disposed on an opposite side of the stepped conduit (126) fromthe first sidewall (118), wherein the second sidewall (120) extendsaround and encloses a second side surface of the aftertreatment device(100), wherein the second sidewall (120) is disposed to provide a narrowgap (130) between the second sidewall (120) and the second side surfaceof the aftertreatment device (100) to receive the flow of cleaning airfrom the stepped conduit (126) over substantially the entire length ofthe aftertreatment device (100) and to direct the flow of cleaning airgenerally downward over the second side surface of the aftertreatmentdevice (100).
 4. The shroud (102) of claim 1, wherein the aftertreatmentdevice (100) is elongate, generally cylindrical, and has a centrallongitudinal axis (104) that extends generally horizontally.
 5. Theshroud (102) of claim 4, wherein the aftertreatment device (100) has atop surface, and wherein the stepped conduit (126) extends generallyhorizontally and is disposed immediately over the top surface of theaftertreatment device (100).
 6. The shroud (102) of claim 5, wherein thefirst downwardly extending step (134, 136, 138) and the seconddownwardly extending step (134, 136, 138) are disposed above the topsurface of the aftertreatment device (100) and are spaced apart alongthe top surface of the aftertreatment device (100).
 7. The shroud (102)of claim 6, wherein the first downwardly extending step (134, 136) isdisposed immediately downstream of a first protrusion (150, 152) thatextends upwardly from the top surface of the aftertreatment device(100).
 8. The shroud (102) of claim 7, wherein the second downwardlyextending step (134, 136) is disposed immediately downstream of a secondprotrusion (150, 152) that extends upwardly from the top surface of theaftertreatment device (100).
 9. The shroud (102) of claim 8, whereineach of the first protrusion (150, 152) and the second protrusion (150,152) comprises an annular ring extending about a circumference of theaftertreatment device (100).